JOHNSON-GROH, CINDY. Department of Biology, Gustavus Adolphus College, 800 W. College Ave., St. Peter, MN 56082. - Population dynamics of Botrychium.
The 2000 field season represented the fourteenth year of monitoring
several species of Botrychium populations in Minnesota, Iowa,
Oregon, and Alaska. A total of 37 plots have been monitored annually
including over 2600 individual tagged plants. Populations fluctuate
independently within and between plots as well as between years and
between plots at different sites. These differences reflect microsite
differences such as soil moisture, herbivory, or mycorrhizae. Fire,
herbivory, herbicide and timber harvest have an immediate impact on
the above-ground sporophytes. The long-term effect of these factors
on below-ground structures (gametophytes and juvenile sporophytes)
appears to be buffered by the large bank of underground structures.
Monitoring reveals populations are fairly resilient and rebound
following perturbations though it may take several years. Using what
we know about the species biology we can model population responses to
natural and man-made perturbations. The model resulting from this
analysis predicts greater stability of populations than might be
concluded from monitoring above-ground plants. This is a consequence
of having a large proportion of the population existing in underground
stages. Even catastrophic elimination of all the underground
gametophyte and sporophyte stages does not inevitably lead to
population extinction because of the importance of the spore bank.
Despite highly variable above-ground population fluctuations,
below-ground stages provide Botrychium populations with a high
degree of buffering against local extinction.
Key words: Botrychium, conservation biology, ecology, population dynamics, population viability analysis, stage-based modeling